Review Question - QID 218192

A 72-year-old female presents to your office having undergone cruciate retaining total knee arthroplasty (TKA) at an outside hospital 9 months ago. For the last several months, she has been having stiffness, pain anterolaterally, and sensations of patellar subluxation with flexion and extension of the knee. On exam, there is no posterior tibial sag or clunk with extension of the knee but there is a subtle J-sign. Radiographs are unrevealing and inflammatory labs are within normal limits. She undergoes a CT scan which leads to you recommending revision TKA. What was the most likely cause of TKA failure?